Level 3 · Advanced sample questions
5 free sample questions on disinfection for the Level 3 · Advanced wastewater treatment operator exam. Try each one, then open the answer to check your work.
One UV bank shows lower intensity than the others. UV transmittance, channel level, lamp power, and lamp age are similar across all banks. A manual sleeve cleaning restores the affected bank, but its automatic cleaning cycle does not. What should be checked first?
Answer: B. Automatic sleeve cleaner
Chlorine feed rate and contact-tank flow stay steady, but residual at the tank outlet falls. A new influent sample has higher ammonia, and the residual measured just after dosing also falls. Which explanation best fits the change?
Answer: A. Increased chlorine demand
A sulfur dioxide ejector discharges into an effluent wet well. Gas feed falls as the wet-well level rises and returns when the level falls. Ejector inlet-water pressure stays steady, the gas supply is adequate, and the vacuum tubing passes its leak test. What should be evaluated first?
Answer: A. Ejector discharge backpressure
A chlorine contact-basin dye test produces an early peak followed by a long, weak tail. Actual flow and operating volume match the detention-time calculation, and release and sampling times were checked. What best explains the result?
Answer: B. Part of the flow takes a short path through the basin
Effluent flow falls while the dechlorination pump stays at a fixed rate. Chlorine residual before dechlorination remains on target. Grab tests confirm rising sulfite throughout the outlet channel, with no detectable final chlorine. Which adjustment best fits these results?
Answer: A. Reduce sulfite feed to match the lower effluent flow
Keep practicing
Operator Master has 5 Level 3 · Advanced disinfection questions, free.
More topics